Cation off-stoichiometric effect on superconducting GdBa₂Cu ₃O_7-δ thin films investigated by Raman spectroscopy

The superconducting properties of cation off-stoichiometric GdB ₂Cu₃O_7-δ (Gd123) thin film grown by pulsed laser deposition method show a strong dependence on target compositions and particularly get worse in case of a ratio Ba/Gd>2. We investigated the effect of cation off-stoichiometric target sample on lattice properties of Gd123 thin films using Raman spectroscopy. In addition to five A_g modes related to ortho-I phase, some additional peaks are seen in the films of Ba/Gd>2. The result implies that the superconducting properties of the films are strongly influenced by the cation off-stoichiometric effect and in connection with the existence of additional peaks.